Richard Moore Posted November 25, 2009 Report Share Posted November 25, 2009 Well...this is new for me. My first residential 3-phase panel. Really a "sub" panel in a 1962 apartment fed from a 100-amp 3-phase service disconnect in the meter room. Nothing more than 2-pole breakers, of course, within the unit's panel. I'm going to report this as a 100-amp 3-phase 120-208 volt service even though, in reality, there is more than the usual 100-amps available. Would you describe it that way? Click to Enlarge 40.38 KB Click to Enlarge 99.86 KB Click to Enlarge 52.36 KB I also had a couple of double-tapped breakers, but this was my "favorite". Check out the connection of the blue wire. Almost got it! Click to Enlarge 40.73 KB Quote Link to comment Share on other sites More sharing options...
Jim Katen Posted November 25, 2009 Report Share Posted November 25, 2009 . . . I'm going to report this as a 100-amp 3-phase 120-208 volt service even though, in reality, there is more than the usual 100-amps available. Would you describe it that way? I would. - Jim Katen, Oregon Quote Link to comment Share on other sites More sharing options...
Jeff Remas Posted November 25, 2009 Report Share Posted November 25, 2009 Don't forget to document and report the location and accessibility of the main disconnect. Quote Link to comment Share on other sites More sharing options...
Marc Posted November 25, 2009 Report Share Posted November 25, 2009 Perhaps get out your multimeter and check the voltages. If you find the voltage to be 208V from one leg to neutral but 120V from the other two legs to neutral then it's an 'unbalanced neutral' configuration which is most popular among residences served by three phase power. A few installations might have a 'balanced' neutral configuration in which case all three lines will measure 120V from neutral. The balanced config has 208V between any two of the three lines which most appliance nameplates accept in lieu of 240V. Marc Quote Link to comment Share on other sites More sharing options...
msteger Posted November 29, 2009 Report Share Posted November 29, 2009 How many of you recommend automatic evaluation of the system by a licensed electrician when you run across 3 phase residential systems? I've seen a few in the past 8 years and each time found a few of the common electrical issues. Since we rarely see 3 phase electrical systems during our inspections and little of our ongoing training seems to ever deal with 3 phase systems, I always recommend complete review and explain to the client why I recommend it. Quote Link to comment Share on other sites More sharing options...
Marc Posted November 30, 2009 Report Share Posted November 30, 2009 I don't think I've seen more than half a dozen in 6 years worth of home inspections, but I do my own evaluations of them. My engineering degree prepares me for it. Would TIJ like me to write on that topic? Marc Quote Link to comment Share on other sites More sharing options...
Marc Posted November 30, 2009 Report Share Posted November 30, 2009 Original quote by Mr. Moore:I'm going to report this as a 100-amp 3-phase 120-208 volt service even though, in reality, there is more than the usual 100-amps available. Would you describe it that way? And by the way, 100 amps is 100 amps. As Freud once said, sometimes a cigar is just a cigar. Marc Quote Link to comment Share on other sites More sharing options...
Brandon Whitmore Posted November 30, 2009 Report Share Posted November 30, 2009 Would TIJ like me to write on that topic Marc, I'd like to learn a little more about 3 phase power. I think I've seen it on 2 inspections so far. Quote Link to comment Share on other sites More sharing options...
Richard Moore Posted November 30, 2009 Author Report Share Posted November 30, 2009 I have actually done quite a bit of wiring of 3-phase panels, but that was back in my Scuba store days, many years and a couple of careers ago. I managed not to kill myself or anyone else. This particular panel didn't really seem that much different than a single-phase except for the extra bus-bar. The arrangement was different but not hard to understand. I agree, sort of, that 100-amps is 100-amps, and it was the way I reported it...BUT...you can't convince me this doesn't have the potential for more load than a 100-amp single phase. For instance, if I had 3 50-amp (208-240v) loads, I could (I think) arrange three 50-amp double pole breakers to handle all those loads simultaneously, and each leg would end up with 100-amps. I could only use two of those in a single-phase 100-amp panel. I'm sure I am missing something, what is it, other than a solid grasp of electrical theory? [:-dunce] Quote Link to comment Share on other sites More sharing options...
Rob Amaral Posted November 30, 2009 Report Share Posted November 30, 2009 I think of it as getting 100A 'from more sources than a single phase'... (from more points on the 'rotating machine')... i.e., tapping similar current, but more 'lines' coming in from the device creating the juice.. (the 'rotating machine'). Electrical stuff gets me dizzy too sometimes.. The rotating machine is the usual source of juice (so far anyway) and that is a turbine somewhere..moved either by steam or water power.. I just say it's a '100A three phase service'.... this is actually has more oomph than single phase... kind of a like 3-man bicycle or something... Quote Link to comment Share on other sites More sharing options...
Marc Posted November 30, 2009 Report Share Posted November 30, 2009 'Introduction to 3-phase electrical systems for home inspectors' coming up. Marc Quote Link to comment Share on other sites More sharing options...
electures Posted December 24, 2009 Report Share Posted December 24, 2009 Well...this is new for me. My first residential 3-phase panel. Really a "sub" panel in a 1962 apartment fed from a 100-amp 3-phase service disconnect in the meter room. Nothing more than 2-pole breakers, of course, within the unit's panel. I'm going to report this as a 100-amp 3-phase 120-208 volt service even though, in reality, there is more than the usual 100-amps available. Would you describe it that way? Click to Enlarge 40.38 KB Click to Enlarge 99.86 KB Click to Enlarge 52.36 KB I also had a couple of double-tapped breakers, but this was my "favorite". Check out the connection of the blue wire. Almost got it! Click to Enlarge 40.73 KB The service is in the meter room. The size of it is based on the main disconnect rating/service entrance conductor ampacity. The panel in the unit is a subpanel. Its ampacity is based on the size of the feeder breaker/conductor ampacity. Quote Link to comment Share on other sites More sharing options...
Richard Moore Posted December 24, 2009 Author Report Share Posted December 24, 2009 The service is in the meter room. The size of it is based on the main disconnect rating/service entrance conductor ampacity. The panel in the unit is a subpanel. Its ampacity is based on the size of the feeder breaker/conductor ampacity. I have no idea why you posted this very basic information, especially a month later, but let's get it right. The service equipment and service disconnect is in the meter room (first photo). The service size to the unit was what I was describing. Quote Link to comment Share on other sites More sharing options...
electures Posted December 24, 2009 Report Share Posted December 24, 2009 The service is in the meter room. The size of it is based on the main disconnect rating/service entrance conductor ampacity. The panel in the unit is a subpanel. Its ampacity is based on the size of the feeder breaker/conductor ampacity. I have no idea why you posted this very basic information, especially a month later, but let's get it right. The service equipment and service disconnect is in the meter room (first photo). The service size to the unit was what I was describing. Sorry for the late post. I just joined. If nobody is allowed to comment on older threads, maybe it should be posted somewhere. My apologies and Merry Christmas!! Quote Link to comment Share on other sites More sharing options...
hausdok Posted December 24, 2009 Report Share Posted December 24, 2009 Hi, No, you can post to any thread you want, at any time. However, keep in mind that your response might be too late to assist the original poster. ONE TEAM - ONE FIGHT!!! Mike Quote Link to comment Share on other sites More sharing options...
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